Pharmacology Cheat Sheet
Endocrine Replacement and Suppression
Endocrine pharmacology for NEET-PG: insulin types, antidiabetic weight effects, PTU in pregnancy, corticosteroid rules, and cabergoline for prolactinoma.
MedNext Academy | 3 min read
Endocrine Replacement and Suppression
Endocrine pharmacology for NEET-PG: insulin types, antidiabetic weight effects, PTU in pregnancy, corticosteroid rules, and cabergoline for prolactinoma.
Endocrine pharmacology covering insulin and antidiabetic drugs, thyroid agents, corticosteroids, and drugs affecting bone and the pituitary axis.
High-yield lines
- Regular (soluble) insulin is the only insulin that can be given intravenously, used in diabetic ketoacidosis.
- Glargine is a peakless long-acting insulin that must never be mixed with other insulins because its acidic pH would precipitate them.
- Insulin degludec has the longest duration of over 42 hours and the lowest hypoglycaemia risk.
- Metformin, SGLT2 inhibitors, and GLP-1 receptor agonists cause weight loss, while insulin, sulphonylureas, and thiazolidinediones cause weight gain.
- Sulphonylureas bind the KATP channel tightly and long, causing fasting hypoglycaemia, unlike the short meal-related action of glinides.
- Levothyroxine is the drug of choice for hypothyroidism due to its 7-day half-life, best taken on an empty stomach before breakfast.
- Propylthiouracil is preferred in the first trimester because methimazole and carbimazole are teratogenic, causing aplasia cutis.
- Propylthiouracil is also preferred in thyroid storm because it blocks peripheral T4 to T3 conversion.
- Corticosteroid adverse effects follow the CUSHINGS mnemonic including cataracts, ulcers, skin thinning, hyperglycaemia, and osteoporosis.
- Assume HPA suppression if prednisolone is given at 20 mg/day or more for 3 weeks, or any dose for over 3 months, and never stop abruptly.
- Cabergoline is the drug of choice for prolactinoma as the most potent D2 agonist, normalising prolactin and shrinking the tumour.
- Fludrocortisone is the drug of choice for mineralocorticoid replacement in Addison's disease.
- Finasteride and dutasteride roughly halve serum PSA and are teratogenic, so women must not handle broken tablets.
- GnRH agonists cause an initial testosterone flare requiring antiandrogen cover in prostate cancer, while GnRH antagonists act immediately without flare.
Mapped competency codes
- PH1.36
- PH1.37
- PH1.38
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This summary maps to PH9-endocrine-pharmacology.
Frequently Asked Questions
Which insulin can be given intravenously?
Only Regular (soluble) insulin; rapid-acting and long-acting analogues are not used IV in DKA.
Why is propylthiouracil preferred in the first trimester?
Because methimazole and carbimazole are teratogenic (methimazole embryopathy with aplasia cutis); the switch is made to methimazole later in pregnancy.
What is the drug of choice for prolactinoma?
Cabergoline, the most potent D2 agonist, which shrinks the tumour and normalises prolactin with twice-weekly dosing.
When should HPA axis suppression be assumed?
With prednisolone 20 mg/day or more for 3 weeks, any dose for over 3 months, or a Cushingoid appearance; never stop abruptly.
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